Method of producing oil in restricted shipping areas

ABSTRACT

TWO LARGE SUBSURFACE STORAGE RESERVOIRS, PREFERABLY UNDERWATER, ARE USED TO ASSIST IN PRODUCING AND TRANSPORTING CRUDE OIL FROM RESTRICTED SHIPPING AREAS. IN ONE AREA WHERE SHIPPING IS RESTRICTED DURING A MAJOR PORTION OF THE YEAR, CRUDE OIL IS PRODUCED INTO A FIRST LARGE SUBSURFACE STORAGE FACILITY. DURING A PERIOD WHEN SHIPPING IS UNRESTRICTED, THE OIL IN THE FIRST SUBSURFACE STORAGE FACILITY IS TRANSFERRED BY WATER TRANSPORTING MEANS TO A SECOND LARGE SUBSURFACE STORAGE FACILITY IN AN UNRESTRICTED SHIPPING AREA. THEREAFTER, THE OIL IN THE SECOND SUBSURFACE STORAGE FACILITY IS TRANSFERRED TO THE CONSUMER WHENEVER REQUIRED BY THE CONSUMER. THE SUBSURFACE STORAGE RESERVOIRS MAY BE IN A CHIMNEY CREATED BY NUCLEAR EXPLOSION.

R. wlLsoN 3,608,315

METHOD OE PRODUGING OIL IN RESTRICTED SHIPPING AREAS Dept'. no', 1U' l Filed Nov. 24, l1957 All INVENTOR.

Robert Wilson AHorney US. Cl. 61-.5 22 Claims ABSTRACT F THE DISCLOSURE Two large subsurface storage reservoirs, preferably underwater, are used to assist in producing and transporting crude oil from restricted shipping areas. In one area where shipping is restricted during a major portion of the year, crude oil is produced into a first large subsurface storage facility. During a period when shipping is unrestricted, the oil in the first subsurface storage facility is transferred by water transporting means to a second large subsurface storage facility in ari unrestricted shipping area. Thereafter, the oil in the second subsurface storage facility is transferred to the consumer whenever required by the consumer. The subsurface storage reservoirs may be ir1 a chimney created by nuclear explosion.

BACKGROUND OF THE INVENTION This invention pertains to a method of using two large subsurface storage facilities to assist in producing crude oil in and transporting crude oil from areas wherein shipping is restricted during a major portion of the year.

In some crude oil producing areas, such as the North Slope of Alaska, shipping is restricted during a major portion of the year. Since the waters in these areas are open to shipping for only a month to a few months of the year, it would be undesirable to limit oil production to only those periods when the waters are open to shipping.

Wells in restricted shipping areas could be produced for a period slightly longer than the period during which the waters are open to shipping by constructing storage facilities in these areas and shipping the oil to the reneries during periods when the water is open to shipping. Such storage facilities have consisted of tanks on land and offshore tanks which are a part of the producing platforms. This method of producing these remotely located wells has many serious drawbacks. A fewexamples of the many drawbacks are that it is necessary to kill the crude oil to store it in this manner. Surface storage tanks and storage facilities on platforms are too small for optimum operation of the producing wells. In addition, periodic shipping causes peak intermittent loads on the refineries and on shipping equipment. In most instances, moreover, the refineries are extremely distant from the restricted shipping area; therefore, it takes a relatively long time for a ship to travel back and forth between the restricted shipping-producing area and the refineries. To unload surface tanks in the allowed time would require a large number of ships because of the long travel time.

As an alternative to` using surface storage facilities in a restricted shipping area, one way to produce the wells on a year-round basis is to install a pipeline from the producing area to the refinery or consumer, A pipeline of this type has the advantage of providing a relatively stable ow of oil to the refinery, but pipelines are extremely expensive and difficult to operate in cold regions. llt is, moreover, impractical to build a pipeline before production rates and `field lives have been established.

Pipeline costs could be reduced by installing a pipe- -line from the restricted shipping area to an unrestricted shipping area. Thereafter, ships could be used to bring the oil to the refinery in a year-round basis. But even this 3,608,315 Patented Sept. 28, 1971 method is extremely expensive. For example, a G50-mile pipeline with limited storage facilities is likely to cost between `67 and 165 million dollars. The other disadvantages associated with long pipelines would be present. This system is also inexible in that the oil must be transported to the consumer within a relatively short time after production.

This invention provides an advantageous way of producing and transporting crude oil in areas ywhere shipping is restricted during a major portion of the year. This method uses two large, subsurface storage facilities; for example, the bulik porosity of large, subsurface, rubble containing volumes. One way to construct a subsurface, rubble containing volume is described in copending application Ser. No. 673,756, led Oct. 9', 1967, now Pat. No. 3,438,204, entitled Underwater Storage Reservoir, by I ames M. Cleary and assigned to the same assignee as this application. A second way of constructing a subsurface, rubble containing, storage volume is described in copending application Ser. No. 682,114, filed Nov. 24, 1967, entitled Underground Storage, by Henry F. Durilap and Robert Wilson, and assigned to the same assignee as this application.

The second 'way for creating the rubble containing volume uses a contained subsurface nuclear explosion to create a rubble containing chimney. In one embodiment of this invention the rubble containing volume is both underground and underwater. It has previously been proposed to use contained nuclear explosions to create an underground storage facility on shore, that is, under dry land; however, it has not Ibeen previously `proposed that a contained nuclear explosion be used to create a storage facility that is underwater as well as underground. Nor has it been proposed to use two spaced apart subsurface storage reservoirs for crude oil handling.

SUMMARY OF THE INVENTION This invention provides another more advantageous way of producing crude oil in areas where shipping is restricted during a major portion of the year. This method provides a new use for two, large subsurface storage reservoirs. It should be noted that the storage facilities are subsurface and that material being acted upony is crude oil.

The first subsurface storage facility is in the area of restricted shipping near the producing area and the second subsurface storage facility is in an area wherein shipping is not considered to be restricted. It should be noted that the second subsurface storage facility may be much closer to the restricted, shipping-producing area than are the consumer or refineries. Oil is produced and stored during a first period in the rst subsurface storage facility at a first rate suitable to the optimum rate for producing the wells. In this invention, oil must be transferred by water transporting means from the rst subsurface storage facility during a second period when the waters near the first subsurface storage facility are operi to shipping. Normally, this second rate of transfer of the stored oil will be greater than the first rate at which oil is added to the first subsurface storage facility. At least part of the oil transferred by water transporting means during the second period is stored in a second subsurface storage facility. The second subsurface storage facility is in an area of unrestricted shipping. Oil is transferred during a third period from the second subsurface storage facility to the consumer at a third rate optimum for consumer operation. In one preferred embodiment, the oil must be `transferred from the second subsurface storage facility by water transporting means to the consumer. When water transporting means are used to transfer oil from both subsurface storage facilities, it is preferred that the distance from the first subsurface storage to the second subsurface storage facility beV less than two-thirds the distance from the first subsurface storage facility to the consumer. Although the three periods will overlap each other, generally, the rst period during which oil is stored in the first subsurface storage facility and the third period during which oil is transferred from the second subsurface storage facility will be greater in duration than the second period during which oil is transferred from the first subsurface storage, Normally, the first rate of oil addition to the first subsurface storage and the third rate of oil transfer from the second subsurface storage will be less than the second rate of oil transfer from the first subsurface storage facility.

The method may include the steps of creating the first and second subsurface storage facilities. Preferably, the subsurface storage facilities will be rubble containing volumes underwater and may be created by detonating a nuclear explosive device far enough underground to be contained. The underground nuclear explosion will also be below water. Two large underwater subsurface storage facilities could be built for less than million dollars.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawing illustrates a preferred sequence of events for producing and transporting crude oil from a restricted shipping area.

DESCRIPTION OF PREFERRED EMBODIMENTS In the drawing, there is illustrated a method of accomplishing more efficient and timely production and transportation of crude oil in areas of restricted shipping using two spaced apart subsurface storage reservoirs to handle the crude oil. Each of the two subsurface storage reservoirs may be created by forming a rubble containing volume below the surface of the earth. Preferably, one or both of the rubble containing, subsurface, storage reservoirs will be underwater. One method of creating this type of storage would be to form a large pile of high bulk porosity objects heavier than water on the bottom of a body of water or on a previously formed impermeable layer on the ocean oor with the top of the pile below the surface of the water. The pile is then covered with a thick seal impermeable enough to contain oil within the pile and two or more conduits placed in the pile. A method for constructing this type of rubble containing, subsurface, underwater storage reservoir is described in copending application Ser. No. 673,756.

A second and more advantageous way of creating one or both of the subsurface, storage reservoirs of extremely large capacity would be to detonate a nuclear explosive device far enough underground to be contained and remote enough from producing equipment to prevent damage to this equipment. Preferably, the nuclear explosion will also be below water. A nuclear explosion is contained when the explosive energy will not cause a crater at the surface of the earth or to the ocean oor. A review of the results of 60 nuclear blast experiments indicates that there is better than a 90 percent chance that the nuclear blast will not crater to the surface if the scaled depth of burial is about 300 feet or deeper. Scaling takes into consideration the yield of the explosive. Some nuclear explosives cratered to the surface of the earth at scaled depths as great as 650 feet; therefore, a scaled depth of burial of more than 650 feet should be used where absolute containment is desired. The scaled depth of burial (SDB) in feet is converted to the actual depth of burial (D) in feet by the following Equation l:

D=(SDB) (W1/3A) bination bomb) far enough below the surface to be contained and of sufficient yield to produce an unstable cavity which will collapse to form the chimney (generally, 5 kilotons and greater). The nuclear explosive is detonated, producing in microseconds high amounts of energy and heat that are unthinkable in any other form of explosive even though it is standard practice to state the yield of a nuclear device in terms of kilotons of TNT (trinitrotoluene).

Upon detonation, an initial cavity is formed as a result of vaporization, melting and crushing of adjacent rock media. The gases within the cavity are at extremely high temperature on the order of millions of degrees and pressure amounting to millions of atmospheres. The expanding energy of the gases compacts and thrusts the surrounding rock radically outward from the shot point creating in fractions of a second a spherical cavity. This high internal pressure expands the cavity until the internal pressure is equivalent to the overburden pressure. At this point the gas pressure supports the overburden, thus preserving the shape of the cavity for a temporary period of time. The radius of the cavity produced by each explosive is a function of the energy yield of the explosive and, to a lesser extent, the depth of burial, the average density of the overlying formations, the vapor forming liquid content of the host rock, and the rock properties. The equation for the cavity radius is R (dh i/4 where R is the cavity radius in feet, C is a constant depending upon rock and fluid content and ranges between 225 and 345, W is the expected yield of the particular nuclear device in equivalent kilotons of TNT, d is the average overburden density in grams per cubic centimeter ranging from about 1.6 to 2.7, and h is is the depth of burial in feet. Suitable estimates for purposes of this invention may be derived by using a value of 290 for the constant C and 2.2 for d.

After a period of time, as heat losses, gas leaks off, and vapor condensation occur, the pressure is reduced until the pressure within the cavity is below the overburden pressure and the fractured rock above the cavity can no longer be supported. The roof of the cavity collapses in r bits and pieces which periodically fall to the bottom of the cavity. A cylindrical column (chimney) of broken rock or rubble develops upward as the cavity fills with rock falling from the roof, Roof collapse continues progressively upward until the volume of interstitial space between the pieces of broken rock in the chimney approximates the original cavity volume before the cavity began to collapse.

The vertical, cylindrical volume of broken rock, is called a chimney. For nuclear explosions in fairly competent formations or in deep formations, the chimney has essentially the same diameter as the original cavity and has a height of about four to seven times the cavity radius. The ratio of chimney height to original cavity radius is, therefore, dependent on the bulk porosity of the broken chimney rock and the cavity volume before collapse. More explicitly, the height of the chimney is about four times the cavity radius divided by three times the net increase in porosity in the rubbled zone stated in a fraction. This fraction ranges between 0.2 and 0.3 and for the formations used here will probably be on the order of 0.25. The interstitial voids or pores formed by the rubble have a high conductivity and provide suitable volume for storage of nonaqueous fluids. After the chimney is formed, it is adapted to oil storage.

As illustrated, first subsurface storage facility `11 is located in a first area of oil production wherein shipping, that is, water transportation by fioating vessels, is restricted for a major portion of the year. In the drawing, this producing area is represented by onshore well 13 and offshore well 15. During a first period oil produced by the wells is produced through suitable production equipment (not shown) and stored in first subsurface storage facility 11. For illustrative purposes, the oil is placed in first subsurface facility 11 by way of fiow system 17 which will include flowlines 19 and 21 for adding and removing oil to the first storage and will also include a ship loading system represented by first loading platform 23 and is not described here in detail.

During a second period when the restricted shipping area is open to shipping, oil is removed from first subsurface storage facility 11 and transferred by water transportation or floating vessel 25 to second subsurface storage facility 27 which is located in a second area that is open to shipping during a major portion of the year. For illustrative purposes, oil is placed in and removed from second subsurface storage facility 27 by way of flowlines 29 and 31 using any sort of above water or below water tanker mooring system which is represented by second platform 33. p

During a third period, oil is removed from the second subsurface storage facility and transferred to a consumer for oil represented by surface equipment 35. Depending on the location of the second subsurface storage facility, all or part of the oil could be transferred to the consumer, e.g., a refinery, via a pipeline. The greatest advantages, however, are derived if the oil is transferred from the second subsurface storage to the consumer by water transportation; for example, by way of tanker 37. Moreover, in order to accomplish still greater advantages, the second subsurface storage facility should be located as close to the restricted shipping area as is practical while maintaining most efficient utilization of transporting vessels. The most efficient location is governed by the distance between the first and second subsurface storage facilities, the length of time that the restricted area is opel to shipping, the production rate of the restricted area, the distance from the second subsurface storage facility and the consumer, and the rate of consumer consumption. The most efficient location for the second subsurface storage facility when water transportation is used as the primary means of transferring oil from the second subsurface stor age facility will be such that the distance between the first and second subsurface storage facilities is less than two-thirds the distance between the first subsurface storage and the consumer.

In order for this method of handling crude oil to operate efficiently, the rate of transfer of oil from first subsurface storage facility 11 to second subsurface storage facility 27 during the second period is greater than the rate at which oil is stored in the first subsurface storage facility during the first period with the first period being a year if the method is conducted for more than a year. All rates are on average barrels per day determined by dividing the total number of barrels handled during the period'by the days in the period. The periods will overlap each other. By the same token, the rate of transfer of oil to the consumer for the second storage during the third period will normally be less than the rate at `which oil is placed in the second storage.

It is to be understood that the specific disclosures herein are illustrative of the preferred invention and that many variations in handling equipment, location, and shipping may be made by those skilled in this art within the scope of the invention as claimed.

What is claimed is:

1. A method of producing and transporting crude oil from restricted shipping areas comprising (a) producing and storing oil during a first period in a first subsurface storage facility in a first area wherein shipping is restricted for a major portioniof the year,

(b) transferring oil by water transportation from said first subsurface storage facility during a second period when said first area is open to shipping to a second subsurface storage facility in a second area which is open to shipping during a major portion of the year, the rate of transfer of oil from said first subsurface storage facility to said second subsurface storage facility during said second period being greater than the rate at which oil is stored in said first subsurface storage facility during said first period, and

(c) transferring oil from said second subsurface storage facility during a third period to a consumer for said oil.

12. The method of claim` 1 wherein in step (c) the oil is transferred from the second subsurface storage facility to the consumer by water transportation.

3. The method of claim 1 wherein the first and the second subsurface storage facilities are created by forming a first and a second rubble containingvolume underwater.

4. The method of claim 3 wherein the first rubble containing Volume is created by detonating a nuclear explosive device far enough underground to be contained, said underground explosion being below water.

5. The method of claim 3 wherein the second rubble containing volume is created by detonating a nuclear explosive device far enough underground to be contained, said underground explosion being below water.

6. The method of claim 3 wherein the method includes the steps of creating the first and the second subsurface storage facilities.

7. The method of claim 6 wherein the first and the second subsurfacestorage facilities are created by forming a first and a second rubble containing volume underwater.

8. The method of claim 7 wherein the firstrubble containing volume is created by detonating a nuclear explosive device far enough underground to be contained, said underground explosion being below water.

9. The method of claim 7 wherein the second rubble containing volume is created by detonating a nuclear explosive device far enough underground to be contained, said underground explosion being below water.

10. The method of claim 1 wherein the first subsurface storage facility is created by forming a first rubble containing volume underwater.

11. The method of claim 10 wherein the first rubble containing volume is created by detonating a nuclear explosive device far enough underground to be contained, said underground explosion being below water.

12. The method of claim 10 wherein the second subsurface storage facility is created by forming a rubble containing volume underwater.

13. The method of claim 12 wherein the second rubble containing volume is created by detonating a nuclear explosive device far enough underground to be contained, said underground explosion being below water.

14. A method of producing and transporting crude oil from restricted shipping areas comprising:

(a) producing and storing oil during a first period in a first subsurface storage facility in a first area wherein shipping is restricted for a major portion of the year, said first subsurface storage facility being underwater,

(b) transferring oil by water transportation from said first subsurface storage facility during a second vpcriod when said first area is open to shipping to a second subsurface storage facility in a second area -which is open to shipping during a major portion of the year, said second subsurface storage facility being underwater, and

(c) transferring oil by water transportation from said second subsurface storage facility 4during a third period to a consumer for said oil.

15. The method of claim 14 wherein the rate of transfer of oil from the first subsurface storage facility to the second subsurface storage facility during the second period is greater than the rate at which oil is stored in said first subsurface storage facility during the first period.

16. The method of claim 14 wherein the distance between the first'and second subsurface storage facilities is less than two-thirds the distance between said first subsurface storage and the consumer.

17. A method of producing and transporting crude oil from restricted shipping areas comprising:

(a) producing and storing oil during a first period in a first subsurface storage facility in a first area wherein shipping is restricted for a major portion of the year,

(b) transferring oil by water transportation from said first subsurface storage facility during a second period when said first area is open to shipping to a second subsurface storage facility in a second area which is open to shipping during a major portion of the year, and

(c) transferring oil by water transportation from said second subsurface storage facility during a third period to a consumer for said oil, the distance between said first and second subsurface storage facilities being less than two-thirds the distance between said first subsurface storage and said consumer.

18. The method of claim 17 wherein the first and the second subsurface storage facilities are created by forming a first and a second rubble containing volume underwater.

19. The method of claim 18 wherein the first rubble containing volume is created by detonating a nuclear explosive device far enough underground to be contained, said underground explosion being below water.

20. The method of claim 18 wherein the second rubble containing volume is created by detonating a nuclear explosive device far enough underground to be contained, said underground explosion being below water.

21. A method of producing and transporting crude oil from restricted shipping areas comprising (a) creating first and second subsurface storage facilities, said rst subsurface storage facility being a first rubble containing volume underwater and being created by detonating a nuclear explosive device far enough underground to be contained, said underground explosion being below water,

(b) producing and storing oil during a first period in a first subsurface storage facility in a first area wherein shipping is restricted for a major portion of the year,

(c) transferring oil by water transportation from said first subsurface storage facility during a second period when said first area is open to shipping to a second subsurface storage facility in a second area which is open to shipping during a major portion of the year, and

(d) transferring oil from said second subsurface storage facility during a third period to a consumer for said oil.

22. A method of producing and transporting crude oil from restricted shipping areas comprising:

(a) creating first and second subsurface storage facilities, said first subsurface storage facility being a first rubble containing volume underwater, said second subsurface storage facility being a second rubble containing volume underwater, and being created by detonating a nuclear explosive device far enough underground to be contained, said underground explosion being below water,

(b) producing and storing oil during a first period in a first subsurface storage facility in a first area wherein shipping is restricted for a maior portion of the year,

(c) transferring oil by water transportation from said first subsurface storage facility during a second pe riod when said first area is open to shipping to a second subsurface storage facility in a second area which is open to shipping during a major portion of the year, and

(d) transferring oil from said second subsurface stor age facility during a third period to a consumer for said oil.

References Cited UNITED STATES PATENTS 2,731,168 1/1956 Watts 6l-46X 3,068,654 12/1962 Warren 6l-0.5

OTHER REFERENCES Oil and Gas Journal of July 6, 1953, p. 42. Oil and Gas Journal of Aug. 17, 1953, p. 84.

JACK SHAPIRO, Primary Examiner U.S. Cl. X.R. 

